Machine description: Mack EM6 6 Cylinder 7.5 L Diesel 275 hp Engine, 8809 Engine hrs, Manual Transmission, 18000 lb Front Axle, 38000 lb Rears, 76500 lb GVWR, Air Ride Cab, 425/65R22.5, Walking Beam Suspension, 232 in Whe... more info about the 1989 Mack RD690S.